A new report released on Thursday says international efforts to protect the ozone layer are a success and have stopped additional ozone losses. The joint World Meteorological Organization and U.N. Environment Program report is the first comprehensive update in four years.

The ozone layer protects life on Earth from harmful levels of ultraviolet rays. Scientists say the shield was thinning during the latter part of the 20th century because of ozone depleting chemicals, such as chlorofluorocarbons found in refrigerants and aerosol sprays.

To save the ozone layer, the international community signed the Montreal Protocol on Substances that Deplete the Ozone Layer, which went into effect in 1989. The treaty calls for phasing out production and consumption of ozone depleting substances.

World Meteorological Organization Research Department Director Len Barrie says the treaty is working.

"It has protected us from severe ozone depletion over the past decade, global ozone, including ozone in the polar regions," Barrie said. "It is no longer decreasing, but not yet increasing. There is, secondly, new information about the two-way link between ozone depletion and ozone processes, et cetera, and climate change. This is a very important advancement in our knowledge."

The report says many substances that deplete the ozone layer also are potent greenhouse gases. Therefore, it says, the Montreal Protocol has provided substantial benefits by reducing climate change.

Atmospheric Environment Research Division Senior Scientific Officer Geir Broothen of the World Meteorological Organization says the ozone layer is projected to return to 1980 levels by the middle of this century.

"This most recent assessment, this 2010 assessment, actually predicts a bit earlier recovery than we foresaw in the 2006 assessment," Broothen said. "And this is linked to this climate change impact, and that increased amounts of greenhouse gases like CO2 [carbon dioxide] and so on in the upper stratosphere will actually speed up the recovery at least in middle latitudes."

The report says the Montreal Protocol also has direct benefits for public health. It says that without the treaty, ozone depleting substances had the potential to increase ten-fold by 2050. And, this in turn, might have led to up to 20 million more cases of skin cancer and 130 million more cases of cataracts.

In addition, the report says, the thinning ozone layer would have caused damage to human immune systems, wildlife and agriculture.